This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The goals of the TrialNet Natural History Study of the Development of Type 1 Diabetes (T1D) are to both gain information about the pathogenesis and natural history of T1D and to facilitate the recruitment and assessment of individuals who might qualify for T1D prevention trials. Importantly, the information obtained from this study will serve to enable the development and implementation of prevention trials. The overall objective of this study is to perform baseline and repeat assessments over time of the metabolic and immunologic status of individuals at risk for T1D in order to characterize their risk for developing T1D, to describe the pathogenetic evolution of T1D, and to increase the understanding of the pathogenetic factors involved in the development of T1D.